As microprocessors advance in complexity and operating rate, the heat generated in microprocessors during operation increases and the demands on cooling systems for microprocessors also escalate. A particular problem is presented by so-called “hotspots” at which circuit elements at a localized zone on the microprocessor die raise the temperature in the zone above the average temperature on the die. Thus it may not be sufficient to keep the average temperature of the die below a target level, as excessive heating at hotspots may result in localized device malfunctions even while the overall cooling target is met. This issue may be applicable to proposed cooling systems in which a coolant such as water is circulated through narrow channels (known as “microchannels”) which are close to or formed in the die.
Another issue that may be encountered in microchannel cooling systems is the total pressure drop experienced by the coolant through its circulation path. The higher the pressure drop, the greater the demands on the pump that circulates the coolant. If higher pumping capacity is required, it may be necessary to include a larger and/or more expensive and/or less reliable pump. Pump size may be especially critical, since space may be at a premium, as is the case in notebook computers and other portable computer systems.
Still another issue that may be encountered in microchannel cooling systems is potential difficulty in connecting tubes for the coolant path to the potentially delicate cover of a microchannel assembly.
Yet another issue relates to fabricating microchannels that have a high aspect ratio (ratio of height to width). Generally speaking, higher aspect ratios in microchannels provide higher heat transfer rates and lower pressure drops. However, the production processes that may be employed in accordance with known practices to form high-aspect-ratio microchannels may be more expensive than other production processes that produce microchannels having smaller aspect ratios.
Another issue is how to reduce pressure drop by shortening the flow length without changing the geometry of the channels (i.e., to keep parallel flow geometry channels). This may allow for improved manufacturability.